The present invention relates to apparatus for extracting samples of product from flow lines or tanks, and in particular to an apparatus which is specially adapted for extracting samples of a slurry from a flow line or tank in which the slurry is maintained under pressure.
Various manufacturing operations require that the immediate or overall composition of a material flowing through a pipe or conduit be monitored. Such monitoring ordinarily is accomplished with apparatus denoted as samplers, which take samples of material from the main body thereof. When a composite sample of the material is required, the sampler may be operated to withdraw a series of small amounts of the material as it passes a sampling point. The individual samples are collected, and represent a composite of the total volume of material.
Other uses for samplers are in on-line analysis applications in which the immediate composition of a material must be determined. For this application, the individual samples of material are not collected as a composite sample, but instead are separately analyzed.
To obtain the samples, some samplers continuously divert streams of material from the flow lines or tanks, and from the diverted streams the samples are removed in various ways. Attempts to withdraw small quantities directly from pipes or tanks, however, have presented many problems not altogether satisfactorily solved. For example, where material receiving holes or slots in samplers are adapted to be extended directly into a pipe, sampled material can build up in such holes and slots and either block the same or contaminate subsequent samples.
Heretofore samplers of the general type have been used to obtain samples of thin or relatively nonviscous liquids which readily flow through the samplers for collection. In recent years, however, a need has arisen to sample materials which are viscous and/or tend to settle out, for example slurries. Conventional samplers do not perform satisfactorily when used to sample such highly viscous liquids or slurries, since the materials are too thick to completely flow through and out of the samplers for collection, and tend to settle out and harden in the samplers and clog the same.
One type of sampler that has been used to obtain samples of a slurry flowing through a pipe comprises a hollow stem which is extendable into and out of the pipe to present an inlet port in the stem to the flow. When the stem is extended into the pipe, slurry flows into the inlet port, through the stem and out of an outlet port from the stem for collection. Since it often happens that the slurry is not homogeneous, the stem may be extended fully across the pipe and then retracted, whereby a cross sectional sample of the slurry is obtained. However, a problem encountered is that when the stem is retracted, residual sampled material remaining in the stem tends to settle out and/or harden, which can contaminate the next sample or clog the stem and completely disable the sampler.